The invention relates to crushing equipment with air-jet, in particular for crushing crystalline materials, consisting of a cylindrical grinding chamber, nozzles and a nozzle carrying crown.
Essentially, crushing equipment with air-jet used in milling practice consists of a horizontally or vertically arranged cylindrical grinding chamber and the nozzles in the cylinder jacket; nozzles are fixed with a thread in the nozzle carrying crown, e.g. the solutions described in British Pat. No. 1 559 139 and U.S. Pat. No. 3,741,485.
The solid, in general crystalline material to be ground introduced into the known crushers is put into a whirling motion under the effect of the gas allowed to stream under high pressure, while comminution is taking place primarily by the mutual percussion of the particles of the material to be ground.
In the known crushers, in the course of the grinding process the solid particles exert a strong abrasive effect not only on each other but on the inner cylinder jacket of the nozzle carrying crown, in particular in the vicinity of the outlet opening of the nozzles. Within a relatively short operational period the smooth surface of the cylinder jacket and the outlet opening of the nozzles become deformed. As a consequence, the streaming pattern also changes and more and more undesired whirls appear resulting in the deterioration of efficiency, while simultaneously with increased abrasive wear the quality of grinding becomes also unacceptable.
To prevent this phenomenon, with the known equipment nozzles and the nozzle carrying crown are to be exchanged frequently which represent very expensive parts of the crushers requiring utmost accurate processing. Considering that a crusher of the middle size contains about 35 to 45 nozzles, the frequent exchange thereof involves considerable economic disadvantages. Essential improvement cannot achieved, even if these strucutral parts are made of highly wear-resistant materials or if a suitable coating is applied thereon (see British Pat. No. 1,362,373).
The aim of the invention is to eliminate disadvantages of the known solutions and simultaneously to develop a crusher with air-jet with economical maintenance.
The aim set can be achieved by assembling the nozzle carrying crown of the known equipment from several parts.